Conventional blind rivets comprise an outer tubular shell or body having an enlarged flange at one end, together with a mandrel associated therewith, such mandrel comprising a cylindrical stem extending through the tubular rivet body so as to be coaxial therewith, the stem having a radially enlarged head at one end for engagement with an end face (tail end) of the rivet body remote from the enlarged flange. The blind rivet is then passed through a preformed hole in a workpiece until the flange engages with the edge of the hole and is held in engagement therewith during a setting operation. During setting, the remote end of the rivet, which is disposed inwardly of the work pieces (the blind side), is then compressed towards the flange by drawing the mandrel stem, and hence the mandrel head, back towards the flange, whereby the deformed portion of the rivet body compresses the work piece therebetween with the flange itself.
Of this type of blind rivet there are two main types. A break stem type blind rivet relies on the mandrel head entering the tail end of the rivet body and being pulled through the rivet body so as to be encapsulated thereby, until the mandrel head meets resistance as the expanded rivet body engages the blind side of the work pieces, whereby the subsequent increase in load on the mandrel stem causes this stem to break at a predefined weakened region so that the mandrel head is retained within the rivet body to form an expanded portion or bulge of the rivet body on the blind side of the work piece thereby compressing the work pieces between this enlarged region and the flange.
Alternatively, a break head type blind rivet relies upon the mandrel head being ejected following setting. In this type of blind rivet, the mandrel head has an abrupt change of section between the mandrel stem and the mandrel head to present a shoulder portion which engages the tail end of the blind rivet to exert a substantially axial force thereon thereby compressing and deforming the end of the rivet against the blind side of the work piece to form a flattened bulge between which the work pieces are again compressed against the flange. Here again a weakened region of the stem will again break, but since the mandrel head has not being drawn into the rivet body it is simply ejected away therefrom when the stem breaks due to the high reaction force between the deformed rivet body and the head.
However, in both these conventional types of blind rivet, a defined or enlarged section of the blind rivet is maintained on the blind side of the work piece presenting a projection which may limit the available workspace on the blind side of the work pieces. This is particularly relevant in the use of blind rivets to manufacture small cabinets, such as those used in the computer industry, whereby the internal projection of a set blind rivet may interfere with the placement of components within such cabinets.
It is therefore an object of the current invention to provide an improved blind rivet which alleviates the aforementioned problems.